PROJECT SUMMARY Neural stem/progenitor cells (NSPCs) are in close communication with vessel-forming endothelial cells (ECs) in the developing brain and adult neural stem cell niches such as the subventricular zone. In addition, transplantation of NSPCs stimulates new vessel formation after stroke, leading to improved functional recovery in rodent models. Despite the importance of NSPC and EC interactions, the complex reciprocal communication between NSPCs and ECs is not well understood, especially in humans. Research on the effect of ECs on NSPCs has focused on EC-secreted factors, which regulate NSPC proliferation, differentiation, and self-renewal. However, the role of EC contact on NSPC phenotype and the interaction of human NSPCs and ECs have not been well studied. We demonstrated that human NSPC (hNSPC) contact with human ECs (hECs) stimulates an increase in the percentage of cells expressing both GFAP and Sox2, which are markers for type B cells, the NSPCs of the adult subventricular zone. The first aim of this study is to determine whether hNSPC contact with hECs promotes a type B cell phenotype by characterizing GFAP+/Sox2+ cells found in co-cultures via staining for additional type B cell markers, single cell RNA sequencing, assessment of cell cycle kinetics and differentiation potential. The second aim is to identify mechanisms involved in this hEC contact-mediated change in hNSPC phenotype by focusing on pathways involved in cell-cell communication such as N-cadherin/b-catenin, integrin signaling, Notch signaling, and Eph/ephrin pathways. NSPCs stimulate vessel formation by ECs. However, the mechanisms by which NSPCs stimulate vessel formation are not understood. Preliminary data using a 3D neurovascular model demonstrates that increased human vessel formation is promoted by hNSPC-secreted factors. The third aim is to identify hNSPC-secreted components stimulating hEC vessel formation by assessing hNSPC conditioned media for potential pro-vasculogenic soluble factors and extracellular vesicles and confirming their role in vessel formation by blocking their effects. Studying the interaction between ECs and NSPCs using human cells can provide better insight into the role of their communication in human brain development, regulation of adult stem cell niches, and repair after brain injury. Animal models have been instrumental for progress in research but have translational limitations due to species differences. Using human cells will allow us to study the interaction of both cell types in a system that may more closely resemble human brain physiology but in a less complex environment. Under this fellowship, I will have the opportunity to work with leading researchers at UC Irvine conducting neuroscience, stem cell, and vessel biology research in a collaborative and supportive environment. To expand my technical skills and knowledge, I will attend workshops, seminars, and conferences on topics important for my research. Research findin...